1. Field of the Invention
This invention relates generally to the adjustable mounting of a motor in respect to a base therefor, and more particularly is directed to the adjustable mounting on a base of a motor whose shaft functions as a capstan in a direct drive type VTR, audio tape recorder or the like.
2. Description of the Prior Art
In a VTR (video tape recording and/or reproducing apparatus) or audio tape recorder, if the axis of the capstan for driving the tape is inclined from the direction extending transversely or at right angles in respect to the longitudinal medium or path of the tape pressed against the capstan by a pinch roller, the tape may undergo relative elongation at one longitudinal edge portion or the other, or the tape may even be displaced from between the capstan and pinch roller. Even if such extreme problems do not occur, smooth movement of the tape will not be attained and, therefore, it is necessary to adjustably position the capstan so that its axis is perpendicular to the longitudinal medium of the tape or to the direction of the path along which the tape is being driven.
In a direct drive VTR or audio tape recorder, the shaft of the driving motor forms the capstan and is rotatably supported in a bearing structure which is usually formed integral with the motor casing. In such a case, adjustment of the capstan axis so as to be precisely perpendicular to the longitudinal medium of the tape being driven thereby is conventionally achieved by providing one or more suitably dimensioned shims or spacers between a peripheral flange on the motor casing and a base of the VTR or audio tape recorder at the time when the motor is being secured in the apparatus, as by screws extending through the flange into the mounting base. Obviously, such adjustment of the relation of the capstan axis to the path of the tape is difficult and time consuming, and, at best, provides a step-by-step, rather than a continuous adjustment. Further, if the flange of the motor casing is positioned above the motor mounting base so that the shims or spacers can be inserted or interchanged relatively easily when effecting the adjustment, the area of the upper surface of the mounting base occupied by the motor is relatively large and, therefore, limits the area of the upper surface of the base that remains available for the mounting of other components thereon. On the other hand, if the peripheral flange of the motor casing is applied against the underside of the mounting base so that the upper surface of the latter is largely available for the mounting of other components thereon, the selective insertion of one or more shims or spacers between the underside of the mounting base and the flange on the motor casing can be realized only with great difficulty, with the result that any adjustment of the axis of the capstan in respect to the tape path is time consuming and expensive to effect.
It has been further conceived to provide a motor for the direct drive of a capstan in a VTR or audio tape recorder in which the bearing housing for the motor shaft or capstan is separate from the remainder of the motor casing. In such case, a peripheral flange of the motor casing is secured directly against the underside of the mounting base, while a flange on the separately formed bearing housing for the motor shaft or capstan which extends over a relatively smaller area is secured to the upper surface of the mounting base and is angularly adjusted relative to the latter by one or more shims or spacers therebetween so as to effect the desired angular relation of the capstan axis in respect to the path of the tape to be driven thereby. However, this last described arrangement is disadvantageous in that adjustment of the capstan axis is accompanied by variations in the relative positioning of the rotor and stator of the motor with the result that uniform motor characteristics cannot be guaranteed.